Biomedical subjects

L Mazzanti

Publications and source records attributed to L Mazzanti.

At least 73 records · Page 4Linked to original sources

PubMed1997

Oligosaccharide organization of the beta-subunits of pig kidney Na+/K+-ATPase.

The distance between the beta-subunits of Na+/K+-ATPase isolated from pig dark red kidney medulla was determined by Förster energy transfer. First, oligosaccharides of the beta-subunit were shown to be labelled with three fluorophores: Lucifer yellow (LY), Lissamine rhodamine B sulfonyl hydrazine (LRSH) and Cascade blue (CB). Further, LY and LRSH were used as the donor and the acceptor, respectively, for Förster energy transfer studies to determine the localization of the beta-subunit in the native enzyme which is known to be formed as a tetramer (alphabeta)2. It was found that the beta-subunits in the functional enzyme complex in the membrane are not localized next to each other but are spatially separated. The distance between fluorophores covalently attached to the beta-subunits was found to be 5.1 nm. This conclusion was confirmed by measurements with another donor-acceptor pair CB-LY. The results also support the idea of a direct interaction of the beta-subunit with the extracellular part of the alpha-subunit. These interactions were modified in the presence of millimolar concentrations of magnesium ions. This indicates a crucial role of magnesium in extracellular interactions between the alpha and beta subunits.

Animals↗

PubMed1996

Effect of biotin on glucokinase activity, mRNA expression and insulin release in cultured beta-cells.

Biotin is known to influence hepatic glucokinase (GK) expression both at a transcriptional and at a translational level. The aim of the present paper was to investigate the effect of biotin on pancreatic GK. For this purpose, RIN1046-38 cells were cultured in the presence of different biotin concentrations for different times; there-after, GK mRNA expression, GK activity and insulin release were studied. Results demonstrated that biotin has a biphasic effect on GK mRNA expression, being stimulatory after short-term treatment and inhibitory after longterm treatment. GK activity was increased after long-term treatment. Insulin release was not affected by biotin treatment. These data suggest that biotin may influence glucose metabolism also by acting directly at the level of beta-cells.

Animals↗

PubMed1996

Na+,K(+)-ATPase of human placenta during gestational hypertension: a biochemical-biophysical study.

1. Na+,K(+)-ATPase is the membrane enzyme catalysing the active transport of Na+ and K+ across the plasma membrane of animal cells. A reduced activity of Na+,K(+)-ATPase has been described in gestational hypertension in a variety of cell types, in agreement with the hypothesis that gestational hypertension can induce membrane transport modifications similar to those reported for essential hypertension. The causes of the reduced Na+,K(+)-ATPase activity are still debated. 2. The aim of the present work was to investigate the molecular mechanism of the reduced enzymic activity in gestational hypertension using as a model Na+,K(+)-ATPase purified from human placenta. Na+,K(+)-ATPase obtained from term placentas of eight healthy pregnant women and eight age-matched women with gestational hypertension was purified as previously described. 3. We observed in gestational hypertension: (i) a significant increase in the activation energies above transition temperature; (ii) a significant decrease in the fluorescence polarization of 1-(4-trimethylaminophenyl)-6-phenyl-1,3,5-hexatriene (i.e. increased fluidity) and an increase in the mean lifetime (modified hydrophobicity); (iii) a lower Kq, suggesting an enzymic structural modification; and (iv) an increased mean lifetime and rotational relaxation time of pyrene isothiocyanate, indicating a modified ATP binding site.

Adult↗

PubMed1996

Activation of endothelial cells during insulin-dependent diabetes mellitus: a biochemical and morphological study.

Plasma membrane lipid dynamics and cellular morphology were evaluated in endothelial cells obtained from umbilical cords of five women affected by insulin-dependent diabetes mellitus (IDDM) and six healthy pregnant women of similar age and gestational age. Endothelial cells were prepared by an adaptation of the method of Jaffe et al. Membrane fluidity was studied by means of the steady-state fluorescence anisotropy (r) of 1-(4-trimethylaminophenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH), a fluorescent probe specifically anchoring at the membrane surface. Fluid phase endocytosis was evaluated by the measurement of the changes in fluorescence intensity of TMA-DPH at various times, owing to the internalization of the fluorescent marker in endocytic vesicles. The morphological and morphometric studies were performed by means of transmission electron microscopy (TEM). Endothelial cells obtained from IDDM women showed: (a) increased fluidity of the superficial region of the plasma membrane; (b) a more active fluid phase endocytosis compared with cells from healthy women; (c) increase in mitochondrial area, Weibel-Palade bodies and rough reticulum with wide cisternae. No statistically significant correlation was found between metabolic control and membrane fluidity and endocytosis. All the observed modifications suggest the presence of endothelial cell activation with membrane reshaping during IDDM. These alterations might play a central role in the pathophysiology of atherosclerosis and microangiopathy associated with diabetes mellitus.

Adult↗

PubMed1995

Morpho-functional modifications of human syncytiotrophoblast plasma membrane during pregnancy induced hypertension.

A decrease of Na+/K(+)-ATPase activity has been reported in syncytiotrophoblast plasma membrane (SPM) obtained from pregnancy induced hypertensive (PIH) women. The aim of the present work was to verify if the reported modifications in activity are due to a decreased number of enzymatic molecules or to a conformational change of the enzyme itself. Morphological studies were performed in order to better understand the relations between the enzymatic protein and the lipid bilayer. Kinetic studies were also performed. SPM obtained from PIH showed: i) an increased affinity of Na+/K(+)-ATPase for ouabain binding, ii) a significant change in the maximum velocity of the enzyme, iii) a higher distribution factor (DF) of intramembrane particles (IMPs) in the exoplasmic face of the membrane, iv) a decreased mean diameter of IMPs both in the protoplasmic and exoplasmic faces, v) a decreased number of IMPs in the exoplasmic face. In conclusion, a conformational modification seems to be at the basis of the decreased Na+/K(+)-ATPase activity during PIH as suggested by binding, ultrastructural and kinetic data herein reported.

Adult↗

PubMed1995

[Treatment of hyperlipidemia in obese patients: monotherapy versus bi-therapy].

OBJECTIVES: Severe hyperlipoproteinaemia (increased LDL, light density lipoproteins, and VLDL, very light density lipoproteins) in patients with high body mass index (BMI) is positively associated with the occurrence of coronary heart disease. This condition requires combined drug regimen because high lipid levels frequently remain after monotherapy and diet. The aim of our study was to investigate the efficacy of combined therapy utilizing the following association: HMG CoA reductase inhibitors plus fibrates. METHODS: We examined 50 patients, males, affected by obesity (BMI > 30) and hyperlipoproteinaemia (phenotype IIB, Fredrickson). The first group, 20 obese subjects with severe dislipidaemia, and the second group, 10 mildly hyperlipidaemic obese patients received bezafibrate 600 mg/d and pravastatin 40 mg/d. The other subjects, all obese and highly dyslipidaemic patients, received monotherapy: 10 patients, bezafibrate 600 mg/d and the rest pravastatin 40 mg/d. Weekly, for ten weeks, we evaluated the following serum parameters: total cholesterol and HDL-cholesterol, triglycerides and apolipoprotein A1 and B. RESULTS: We observed no significant changes in HDL-cholesterol and apolipoprotein levels, while an important reduction in total cholesterol and triglycerides, induced by combined therapy, was particularly evident in those patients with the higher lipidic alterations, compared with the additive effects of single drugs. CONCLUSIONS: The data show that this combined treatment could be proposed for these subjects to reduce hyperlipidaemia and the risk of premature atherosclerosis.

Adult↗

PubMed1995

Biochemical-morphological modifications of platelet membranes during pregnancy-induced hypertension.

A platelet (PLT) function modification has been reported in normal pregnancies compared with the nonpregnant condition and it has been hypothesized to play a central role in the pathogenesis of pregnancy-induced hypertension (PIH). The aims of the present study were (i) to evaluate the lipid composition, fluidity at different depths, transport functions, and ultrastructural features of the PLT membrane in PIH and (ii) to ascertain whether similar modifications may be determined by the state of pregnancy in comparison with the nonpregnant condition. The platelets of healthy pregnant women (HPW) showed: (i) an increase in Ca2+ ATPase activity, (ii) a decreased fluidity of the deeper site of the membrane, (iii) a reduced cholesterol concentration, with an increased ratio between unsaturated and saturated fatty acids; (iv) a decreased intramembranous particles (IMP) distribution factor (DF) of the plasma membrane E face in comparison with healthy nonpregnant women. When comparing women affected by PIH with HPW, we observed (i) reduced Na+/K+ ATPase activity and enhanced Ca2+ ATPase activity and intraplatelet calcium concentrations, (ii) an increased membrane fluidity, (iii) an increased cholesterol concentration and ratio between unsaturated and saturated fatty acids, (iv) a reduction of the IMP number and the DF. Pregnancy produces a deep modification of the platelet plasma membrane, and PIH produces a more pronounced alteration of the maternal platelets, which can be responsible for the observed modifications in placental blood flow and in the fetomaternal exchange.

Blood Platelets↗

PubMed1995

Frequency, clinical and laboratory features of thyroiditis in girls with Turner's syndrome. The Italian Study Group for Turner's Syndrome.

A total of 478 patients, mean age 15.5 (3.6-25.3) years, suffering from Turner's syndrome, were studied in order to determine the frequency of autoimmune thyroiditis, which is defined as the presence of antithyroid antibodies (AT-Ab) and typical ultrasound findings. We found 106 (22.2%) patients positive for AT-Ab and of those 49 (10%) also had positive ultrasound findings, and were therefore considered to be affected by thyroiditis. This frequency is significantly higher (p < 0.001) than that seen in the normal population. Goitre was detected on clinical examination in only 16 (33%) and by ultrasound in 19 (39%) patients. Hormonal evaluation showed that 17 patients were euthyroid, 27 had compensated hypothyroidism, 2 were hypothyroid and 3 were in a hyperthyroid phase. Clinical signs or symptoms of hypothyroidism were absent in all hypothyroid patients. In patients with thyroiditis, neither a higher frequency of malformations and autoimmune diseases nor a correlation with karyotype, oestrogens or growth hormone therapy was found.

Adolescent↗

PubMed1995

The human umbilical vein in normal, hypertensive and diabetic pregnancies: immunomorphological and ultrastructural evidence.

Mother-fetus exchanges at the placental level are found to be altered in women affected by hypertensive or diabetic pregnancies following the onset of microenvironmental, circulatory, trophic or tissue disorders. Our aim was therefore to assess the alterations occurring within the umbilical cord, particularly its venous endothelial component and underlying smooth muscle layer, using transmission (TEM) and scanning electron microscopy (SEM) and immunohistochemical analyses. Immunohistochemical data appear to support the ultrastructural evidence for an activated state of these vascular structures, in both conditions (hypertension and diabetes). Furthermore, mainly during diabetic pregnancies, extracellular matrix molecules such as tenascin and fibronectin also quantitatively increase at the vein wall level. The umbilical cord seems to be a structure capable of responding actively to abnormal microenvironmental conditions which seriously threaten the health of the fetus and also the mother herself.

Cell Adhesion Molecules↗

PubMed1995

Transdermal estradiol and medroxyprogesterone acetate in hormone replacement therapy are both antioxidants.

We have evaluated the effects of the different components of hormone replacement therapy (HRT) on the production of free radicals in platelet membranes from menopausal women. The study included 12 women in menopause for at least 6 months to a maximum of 4 years. First, the effect was determined of progestin only during the administration of 20 mg/day medroxyprogesterone acetate for 5 days. The peroxide production level was measured on day 0 and day 5. The second set of experiments was carried out in the first month of cyclic HRT with transdermal estradiol 50 micrograms/day from day 1 to day 25 and medroxy-progesterone acetate from day 13 to day 25. In this experiment, the peroxide level was evaluated on days 0, 12 and 25. A significant reduction of peroxide level was observed after oral medroxyprogesterone acetate administration. During HRT, we observed a similar reduction in lipid oxidation at the peak of the estrogen effect, and a further decrease with the administration of medroxyprogesterone acetate. It is concluded that reduction of lipid peroxidation during HRT is not only due to estrogens, but also depends upon the combined action of sex steroids. This observation justifies not only the combined regimen (estrogens plus progestin) in HRT, but also the positive effects of progestins alone on patients who cannot use estrogens.

Administration, Cutaneous↗

PubMed1995

Modifications of functional and physico-chemical properties of rat ileal plasma membranes.

A membrane fraction enriched with plasma membranes was isolated from rat ileal brush-border cells before and after five-day starvation of the animals. Cholesterol/phospholipid ratio of the standard cell membranes decreased highly significantly (0.42 to 0.18), as did the microviscosity of the membranes determined by polarization of fluorescence (0.187 to 0.142). Concomitantly, the specific activity of Na,K-ATPase in the basolateral membranes significantly increased (59 to 83 mumol ATP hydrolyzed per mg protein per min).

Animals↗

PubMed1994

A biochemical-morphological study on microvillus plasma membrane development.

The microvillus plasma membrane of the human placental syncytiotrophoblast at term has been extensively studied, while little is known about the characteristics of its development. The aim of the present work was to compare functional and structural properties of this membrane at early and term gestational age. Ten normal term placentas (40 weeks) and ten placentas at 10 weeks of gestational age were studied. The Na+/K+-ATPase activity is significantly decreased in the syncytiotrophoblast plasma membrane obtained from term placentas as compared to the early ones, with significant variation of maximum velocity (Vmax). The microviscosity, evaluated by the P parameter of DPH and Sn parameters of 5- and 16-NS, is increased in the term placentas compared to the early placentas. This alteration is accompanied by an increased cholesterol to phospholipids ratio in term placentas, while there is a decreased unsaturated to saturated fatty acid ratio. As follows from morphological studies, an increased mean diameter in the E face was observed in the term placenta with respect to the early placenta. The distribution factor DF, which indicates the particle aggregation state, decreased in the E face in the term placenta as compared to the early one. The present biochemical morphological study shows that a deep modification of the membrane is at the basis of the syncytiotrophoblast plasma membrane development.

Female↗

PubMed1994

Pregnancy induced hypertension: a role for peroxidation in microvillus plasma membranes.

It has been recently hypothesized that in PIH a placental oxidant-antioxidant imbalance might cause the release of lipoperoxidation products into the circulation, with subsequent damage of endothelial cell membranes. In this hypothesis the endothelial cell and further increase in circulating lipoperoxide levels, which are by themselves able to induce smooth muscle constriction and increased pressor responsiveness to angiotensin II. In order to investigate this issue, we studied the basal content of lipid peroxides in terms of malondialdehyde (MDA) in the syncytiotrophoblast plasma membranes (SPM) from PIH women. Moreover, we investigated the susceptibility to peroxidation of SPM using an in vitro oxidative stress as a tool to verify the predisposition to the in vivo development of peroxidation products. The fatty acid composition of the membranes was also analyzed. Microvillus membrane lipoperoxide concentrations were significantly increased in PIH women (62.8 +/- 7.6 ng MDA/mg prot) compared with healthy pregnant subjects (37.6 +/- 4.8 ng MDA/mg prot; p < 0.01). The formation of TBARS under the action of phenylhydrazine was significantly greater in PIH women (90.3 +/- 7.4 mmol MDA/mol cholesterol) than in normal pregnant subjects (68.6 +/- 6.4 mmol MDA/mol cholesterol; p < 0.01). In PIH microvillus membrane we also observed a significant increase of the content of polyunsaturated arachidonic acid. The increased susceptibility to oxidative stress of SPMs from PIH women might be due either to reduced antioxidant systems or to an abnormality of the lipid composition of the membrane.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1994

Human hypertensive placenta contains an increased amount of Na,K-ATPase with higher affinity for cardiac glycosides.

Placentas of women suffering from pregnancy-induced hypertension (PIH) were found to contain a greater amount of Na,K-ATPase molecules, estimated from anthroyl ouabain binding, than normotensive individuals. Both the microsomal fraction of placental cells and purified Na,K-ATPase showed an increased affinity for the specific inhibitor ouabain which, in the case of the microsomes, bound with a dissociation constant of 0.9 nM as compared with 3.4 nM in the controls. Likewise, the dissociation constant of the ouabain complex with purified Na,K-ATPase was about 3.5 times lower in the hypertensive patients. The differences are apparently caused by a different microenvironment of the ouabain-binding site, as reflected in the quantum yield of bound anthroyl ouabain. If an endogenous digitalis-like factor is present in the body fluids to regulate Na,K-ATPase activity, the present results render its role quite plausible.

Adult↗

PubMed1994

Modified fluidity and lipid composition in lipoproteins and platelet membranes from diabetic patients.

The interaction between lipoproteins and the platelet membrane has been proved to cause a modification in cellular functions. We studied 12 men with insulin-dependent diabetes mellitus (IDDM), 14 men with noninsulin-dependent diabetes mellitus (NIDDM), and 26 age-matched healthy men on the same diet. We determined fluidity by measuring the fluorescence polarization (P) of the probe 1,6-diphenyl-1,3,5-hexatriene (DPH) both in platelet membranes and in lipoproteins isolated by ultracentrifugation in NaBr density gradient. The lipid composition of lipoproteins and of platelet membranes was determined by enzymatic methods. The fluidity of platelet membranes was significantly increased both in patients affected by NIDDM and in subjects with IDDM compared with normal subjects. Low-density lipoproteins (LDL) showed an increased fluidity only in NIDDM patients. A percent increase in the triglyceride content was observed in all lipoprotein fractions in diabetic subjects. Increased phospholipid content was found in the platelet membranes from IDDM and NIDDM patients. The change in LDL fluidity observed in NIDDM patients might determine altered interactions between the lipoprotein and cellular receptors. The role of lipoproteins in the modulation of the platelet membrane properties in diabetes mellitus deserves further studies.

Adult↗

PubMed1994

Increased susceptibility to lipid oxidation of low-density lipoproteins and erythrocyte membranes from diabetic patients.

The aim of the present study was to determine if low-density lipoproteins (LDLs) and red blood cell (RBC) membranes from diabetic patients present an increased susceptibility to lipoperoxidation, which might be related to the increased incidence of atherosclerosis in diabetes. LDLs and RBC membranes were isolated from 11 insulin-dependent (IDDM) and 18 non-insulin-dependent diabetic (NIDDM) patients and exposed to a peroxidative stress by incubation with phenylhydrazine. The susceptibility to peroxidation was determined by measuring the production of thiobarbituric acid-reactive substances (TBARS) after the incubation. The following parameters were also evaluated: plasma glucose, triglycerides (TG), phospholipids (PL), total and high-density lipoprotein (HDL) cholesterol, apolipoprotein (apo) A-I, apo B, hemoglobin A1c (HbA1c), LDL PL and cholesterol, LDL fatty acid composition, and RBC membrane PL and cholesterol. Although they were apparently normolipidemic, diabetic patients showed an increased susceptibility to peroxidation in LDLs and erythrocyte membranes as compared with control subjects. The amount of arachidonic acid in LDLs and the PL concentration of RBC membranes from diabetic patients were significantly higher than in normal subjects. The increased lipoperoxidability of both RBC membranes and LDLs might play a central role in the pathogenesis of the vascular complications of diabetes mellitus.

Adult↗

PubMed1994

Spontaneous growth and pubertal development in Turner's syndrome with different karyotypes.

We studied spontaneous growth and pubertal development in 205 girls with Turner's syndrome, aged 1 month to 28.16 years, according to different karyotypes: 45,X (52%), X-mosaicism (12%), X-structural abnormalities (36%). Data on height, weight, height velocity, bone age and pubertal development were collected yearly in a mixed longitudinal and cross-sectional mode. Pelvic ultrasonography was performed in 133 patients, 46 of whom had contact breast thermography. Standards for height and height velocity (1-20 years) showed no differences when compared with other studies. Some differences were found when these data were subdivided by karyotype. In fact, X-mosaicism subjects had a pubertal growth spurt between 8 and 12 years of age. The spurt observed in this group cannot be justified by the more frequent presence of residual ovarian activity alone. It also appears in patients without ovaries and confirms the influence of a genetic factor on the X-chromosome. In spite of this spurt, the greatest final height was reached by 45,X subjects. X-mosaicism girls had more frequent spontaneous breast development linked to a higher percentage of visible ovaries. In this group the age of the first pubertal signs was similar to that of normal subjects and occurred much earlier than in the other groups.

Adolescent↗

PubMed1994

Reduced Na(+)-K(+)-ATPase activity and plasma lysophosphatidylcholine concentrations in diabetic patients.

A fraction from normal human plasma inhibiting Na(+)-K(+)-ATPase has been recently identified as lysophosphatidylcholine (LPC). The aim of this study was to investigate the existence of a relationship between the activity of the cellular membrane Na(+)-K(+)-ATPase and plasma LPC in human diabetes. We studied 10 patients with insulin-dependent-diabetes mellitus (IDDM), 14 patients with non-insulin-dependent diabetes mellitus (NIDDM), and 10 sex- and age-matched control subjects. Plasma LPC concentrations were increased in both IDDM and NIDDM patients compared with control subjects. Na(+)-K(+)-ATPase activity was reduced in both groups of patients in erythrocyte and platelet membranes. There was a significant correlation between the concentrations of plasma LPC and Na(+)-K(+)-ATPase activity in both erythrocyte and platelet membranes (P < 0.01). To investigate the effect of LPC on the enzyme, Na(+)-K(+)-ATPase activity was determined in erythrocyte membranes obtained from six healthy subjects after in vitro incubation with increasing concentrations of LPC (1-10 microM). Enzymatic activity was significantly reduced by in vitro LPC at a concentration of 2.5 microM, with a further decrease at 5 microM. These data suggest that the decrease in Na(+)-K(+)-ATPase activity in diabetes might be due to increased LPC concentrations.

Adult↗